Soviets will be screwed. Allies can pick and choose where to land.
Soviets will be successful at first.
Allies hold in southern France and northern Italy. As they perform a fighting retreat, evacuations and re-land in southern France near Spain. The goal is to hold Spain (Franco sees writing on wall and joins allies), Italy and Iran oilfields while Japan is finished off.
Priority 1 is Japan
2 is Iran
3. Defend turkey
4 defend Spain and Italy
Soviets are stopped cold in the Pyrenees, Italy and in Iran. The middle east is where allied troops are rushed to to prevent soviet access to persian gulf.
After these objectives are met what next?
After Japan, obviously Soviet far east is open. But it is minimal value and sooner or later logistics come into play. But usa would secure Vladivostok, Manchuria and drive to lake Baikal region.
From southern Iran, allies secure northern Iran, Iraq, and may drive to Baku. But mountains and logistics will come into play again. But not a drop of Caucus or Romanian oil get to Soviet refineries.
Perhaps the allies build up in Italy and drive north to Baltic. Or land along black sea coast of Ukraine (Turkey entered war in 1945 on allied side.)
Meanwhile, Soviet resistance groups everywhere play havoc behind the lines. Stalin has a lot of enemies in eastern Europe, free France, German underground, Baltic region ...
Allied air superiority targets Soviet production and logistics. As soon as Soviet cities are within reach of B29's, they are wiped out.
Soviets were counting on quick victory and peace over war weary England and USA distracted by Japan. They did not figure on allied resolve being so strong.
Soviets are given no time to consolidate and build defences.
Allies can pick and choose where to land and exploit.
Ultimately, in 1951 Moscow is captured. There is no Soviet union.
Soviet union and Russia are broken up.
USA administers Sakhalin, Kuriles, Kamchatka, perhaps even all of Soviet far east.
Finland gets their claims back.
East Prussia??? Could it be given to Britain? Or back to Germany?
Globally - what is effect
China - nationalists win
British and French empires for decolonisation in Africa and Asia.
India and Pakistan become independent
British and French leave middle east
French and Vietnamese still clash. Vietnamese win. USA does not back France.
USA ensures Philippines are independent as well as Korea.
USA rebuilds Europe including the resulting Soviet/Russian states
No space race - moon landings occur in 1980's
But perhaps with no cold war, bush wars of Africa and Asia are less as colonialism ends.